The problem started after I went out shut the car off, then when i went to start it again, it was running rough and the idle was up and down.
I found that I had a dead spark plug, so that cured the rough running part, but the idle was still not right.

When I first start the car when its cold, it revs up to about 2000 Rpm for 1 min or so, then gradually drops down to idle, when I hit the throttle, it revs up, but it slowly comes down to idle.
When I am driving down the road, I can cruise at 40 kmph without touching the gas.
I read that the Idle control valve is a common problem, so I was able to get a supossidly good used one and it didnt change a thing. also i was thinking vacuum leak, so I used accetylene and found no leaks. Also though there were a few spots I could not get to.
Any suggestions would be very much appreciated.

 

The engine is a 4.0L OHV